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New theory provides alternative to big bang

Posted April 26, 2002; 11:29 a.m.

by etu

A new theory of the universe suggests that space and time may not have begun in a big bang, but may have always existed in an endless cycle of expansion and rebirth.

Princeton physicist Paul Steinhardt and Neil Turok of Cambridge University described their proposed theory in an article published April 25 in an online edition of Science.

The theory proposes that, in each cycle, the universe refills with hot, dense matter and radiation, which begins a period of expansion and cooling like the one of the standard big bang picture. After 14 billion years, the expansion of the universe accelerates, as astronomers have recently observed. After trillions of years, the matter and radiation are almost completely dissipated and the expansion stalls. An energy field that pervades the universe then creates new matter and radiation, which restarts the cycle.

The new theory provides possible answers to several longstanding problems with the big bang model, which has dominated the field of cosmology for decades. It addresses, for example, the nagging question of what might have triggered or come "before" the beginning of time.

The idea also reproduces all the successful explanations provided by standard picture, but there is no direct evidence to say which is correct, said Steinhardt, a professor of physics. "I do not eliminate either of them at this stage," he said. "To me, what's interesting is that we now have a second possibility that is poles apart from the standard picture in many respects, and we may have the capability to distinguish them experimentally during the coming years."

The big bang model of the universe, originally suggested over 60 years ago, has been developed to explain a wide range of observations about the cosmos. A major element of the current model, added in the 1980s, is the theory of "inflation," a period of hyperfast expansion that occurred within the first second after the big bang. This inflationary period is critical for explaining the tremendous "smoothness" and homogeneity of the universe observed by astronomers, as well as for explaining tiny ripples in space that led to the formation galaxies.

Scientists also have been forced to augment the standard theory with a component called "dark energy" to account for the recent discovery that the expansion of the universe is accelerating.

The new cyclic model replaces inflation and dark energy with a single energy field that oscillates in such a way as to sometimes cause expansion and sometimes cause stagnation. At the same time, it continues to explain all the currently observed phenomena of the cosmos in the same detail as the big bang theory.